1. Field of the Invention
The invention relates to a vehicle seat in which a headrest is attached to a seat back.
2. Description of the Related Art
Usually, a headrest is attached to a seat back of a vehicle seat, in order to protect the head of a seated user in the event that the vehicle is rear-ended. The headrest is usually arranged at a position that is slightly apart from the head of the seated user in the rearward direction such that the head of the seated user is prevented from inappropriately contacting the head rest when the vehicle is driven.
Japanese Patent Application Publication No. JP(A) 2001-163099 discloses a known vehicle seat of the above-mentioned type. According to the technology disclosed in Japanese Patent Application Publication No. JP(A) 2001-163099, when a vehicle is rear-ended and the upper body of a seated user moves rearward in reaction to the rear-end collision, a load generated by this rearward movement is transmitted to right and left headrest holders (headrest supporting brackets) and therefore a headrest is moved upward while being tilted forward, whereby the head and the neck of the seated user are protected.
In the vehicle seat disclosed in Japanese Patent Application Publication No. JP(A) 2001-163099, passive means for transmitting the load generated by the rearward movement of the upper body of the seated user to the right and left headrest holders is formed mainly of a belt provided in a center portion of a seat back, which is located between the right and left headrest holders. The load generated by the rearward movement of the upper body of the seated user is transmitted to the right and left headrest holders via the belt provided in the center portion. Therefore, the loads received by the right and left headrest holders are likely to be unequal. As a result, the situation may be caused in which the headrest is tilted in an undesired direction, and cannot be smoothly moved upward while being tilted forward.
If the width of the belt is increased such that the ends of the belt are located near the right and left headrest holders, undesired tilting of the headrest might be prevented. However, an increase in the belt width causes other problems such as an increase in cost and an increase in weight.